package org.bouncycastle.bcpg;

import java.io.*;
import java.util.Vector;

/**
 * reader for Base64 armored objects - read the headers and then start returning
 * bytes when the data is reached. An IOException is thrown if the CRC check
 * fails.
 */
public class ArmoredInputStream
    extends InputStream
{
	/*
	 * set up the decoding table.
	 */
	private static final byte[] decodingTable;

	static
	{
		decodingTable = new byte[128];

		for (int i = 'A'; i <= 'Z'; i++)
		{
			decodingTable[i] = (byte)(i - 'A');
		}

		for (int i = 'a'; i <= 'z'; i++)
		{
			decodingTable[i] = (byte)(i - 'a' + 26);
		}

		for (int i = '0'; i <= '9'; i++)
		{
			decodingTable[i] = (byte)(i - '0' + 52);
		}

		decodingTable['+'] = 62;
		decodingTable['/'] = 63;
	}

	/**
	 * decode the base 64 encoded input data.
	 *
	 * @return the offset the data starts in out.
	 */
	private int decode(
		int		in0,
		int		in1,
		int		in2,
		int		in3,
		int[]	out)
		throws EOFException
	{
		int	b1, b2, b3, b4;

		if (in3 < 0)
		{
			throw new EOFException("unexpected end of file in armored stream.");
		}

		if (in2 == '=')
		{
			b1 = decodingTable[in0] &0xff;
			b2 = decodingTable[in1] & 0xff;

			out[2] = ((b1 << 2) | (b2 >> 4)) & 0xff;

			return 2;
		}
		else if (in3 == '=')
		{
			b1 = decodingTable[in0];
			b2 = decodingTable[in1];
			b3 = decodingTable[in2];

			out[1] = ((b1 << 2) | (b2 >> 4)) & 0xff;
			out[2] = ((b2 << 4) | (b3 >> 2)) & 0xff;

			return 1;
		}
		else
		{
			b1 = decodingTable[in0];
			b2 = decodingTable[in1];
			b3 = decodingTable[in2];
			b4 = decodingTable[in3];

			out[0] = ((b1 << 2) | (b2 >> 4)) & 0xff;
			out[1] = ((b2 << 4) | (b3 >> 2)) & 0xff;
			out[2] = ((b3 << 6) | b4) & 0xff;

			return 0;
		}
	}

	InputStream	in;
	boolean		start = true;
	int[]				outBuf = new int[3];
	int				bufPtr = 3;
	CRC24			crc = new CRC24();
	boolean		crcFound = false;
	boolean		hasHeaders = true;
	String			header = null;
	boolean		newLineFound = false;
	boolean		clearText = false;
	boolean		restart = false;
	Vector			headerList= new Vector();
	
	/**
	 * Create a stream for reading a PGP armoured message, parsing up to a header 
	 * and then reading the data that follows.
	 * 
	 * @param in
	 */
    public ArmoredInputStream(
    	InputStream	in) 
    	throws IOException
    {
        this.in = in;
        
		if (hasHeaders)
		{
			parseHeaders();
		}

		start = false;
    }
    
    /**
     * Create an armoured input stream which will assume the data starts
     * straight away, or parse for headers first depending on the value of 
     * hasHeaders.
     * 
     * @param in
     * @param hasHeaders true if headers are to be looked for, false otherwise.
     */
	public ArmoredInputStream(
		InputStream	in,
		boolean		hasHeaders) 
		throws IOException
	{
		this.in = in;
		this.hasHeaders = hasHeaders;
		
		if (hasHeaders)
		{
			parseHeaders();
		}

		start = false;
	}
	
    public int available()
    	throws IOException
    {
    	return in.available();
    }
    
	private boolean parseHeaders()
		throws IOException
	{
		header = null;
		
		int			c;
		int			last = 0;
		boolean	headerFound = false;
		
		headerList = new Vector();
		
		//
		// if restart we already have a header
		//
		if (restart)
		{
			headerFound = true;
		}
		else
		{
			while ((c = in.read()) >= 0)
			{
				if (c == '-' && (last == 0 || last == '\n'))
				{
					headerFound = true;
					break;
				}
	
				last = c;
			}
		}

		if (headerFound)
		{
			StringBuffer	buf = new StringBuffer("-");
			
			if (restart)	// we've had to look ahead two '-'
			{
				buf.append('-');
			}
			
			while ((c = in.read()) >= 0)
			{
				if (last == '\n' && c == '\n')
				{
					break;
				}
				if (c == '\r' || c == '\n')
				{
					headerList.addElement(buf.toString());
					buf.setLength(0);
				}
				if (c != '\r')
				{
					last = c;
					if (c != '\n')
					{
						buf.append((char)last);
					}
				}
			}
		}
		
		header = (String)headerList.elementAt(0);
		clearText = header.equals("-----BEGIN PGP SIGNED MESSAGE-----");
		newLineFound = true;
		
		return headerFound;
	}

	/**
	 * @return true if we are inside the clear text section of a PGP
	 * signed message.
	 */
	public boolean isClearText()
	{
		return clearText;
	}
	
	/**
	 * Return the armor header line (if there is one)
	 * @return the armor header line, null if none present.
	 */
	public String	getArmorHeaderLine()
	{
		return header;
	}
	
	/**
	 * Return the armor headers (the lines after the armor header line),
	 * @return an array of armor headers, null if there aren't any.
	 */
	public String[] getArmorHeaders()
	{
		if (headerList.size() <= 1)
		{
			return null;
		}
		
		String[]	hdrs = new String[headerList.size() - 1];
		
		for (int i = 0; i != hdrs.length; i++)
		{
			hdrs[i] = (String)headerList.elementAt(i + 1);
		}
		
		return hdrs;
	}
	
    public int read()
    	throws IOException
    {
		int	c;

		if (start)
		{
			if (hasHeaders)
			{
				parseHeaders();
			}

			start = false;
		}
		
		if (clearText)
		{
			c = in.read();

			if (c == '\n')
			{
				newLineFound = true;
			}
			else if (newLineFound && c == '-')
			{
				c = in.read();
				if (c == '-')			// a header, not dash escaped
				{
					clearText = false;
					start = true;
					restart = true;
				}
				else                   // a space - must be a dash escape
				{
					c = in.read();
				}
				newLineFound = false;
			}
			else
			{
				newLineFound = false;
			}
			return c;
		}
		
		if (bufPtr > 2)
		{
			c = in.read();
			if (c == '\n' || c == '\r')
			{
				c = in.read();
				if (c == '\n')
				{
					c = in.read();
				}

				if (c < 0)				// EOF
				{
					return -1;
				}
	
				if (c == '=')			// crc reached
				{
					bufPtr = decode(in.read(), in.read(), in.read(), in.read(), outBuf);
					if (bufPtr == 0)
					{
						int i = ((outBuf[0] & 0xff) << 16)
								| ((outBuf[1] & 0xff) << 8)
								| (outBuf[2] & 0xff);

						crcFound = true;

						if (i != crc.getValue())
						{
							throw new IOException("crc check failed in armored message.");
						}

						return -1;
					}
					else
					{
						throw new IOException("no crc found in armored message.");
					}
				}
				else if (c == '-')		// end of record reached
				{
					while ((c = in.read()) >= 0)
					{
						if (c == '\n')
						{
							break;
						}
					}

					if (!crcFound)
					{
						throw new IOException("crc check not found.");
					}

					return -1;
				}
				else				   // data
				{
					bufPtr = decode(c, in.read(), in.read(), in.read(), outBuf);
				}
			}
			else
			{
				if (c >= 0)
				{
					bufPtr = decode(c, in.read(), in.read(), in.read(), outBuf);
				}
				else
				{
					return -1;
				}
			}
		}

		c = outBuf[bufPtr++];

		crc.update(c);

		return c;
	}
}
